Offshore oil and gas drilling operations utilize pressurized fluid systems for a number of applications and purposes, and such fluid systems employ a variety of couplings and connections. One type of connection is known as a "stab" connection wherein a conduit is telescopingly received within a cylindrical bore and the conduit is then sealed with respect to the bore after insertion is completed. Oil exploration and drilling apparatus often employs heads or manifolds on which a plurality of conduits are mounted having stab type seal units wherein a plurality of fluid type connections are simultaneously achieved. As such connections often occur several hundreds of feet below the water surface, and may be exposed to very high pressures, it is most important that the connections be highly dependable and effective, and require a minimum of maintenance.
Known seal assemblies for use in such applications have not been completely satisfactory. For instance, previous seal assemblies may score the bore as the stab conduit is being received therein, and some seal assemblies require close regulation of the degree of insertion of the seal assembly into the bore in order to produce an effective seal. Such accuracy under the conditions of installation are often very difficult to achieve. Further, lateral or angular variations may occur between the stab conduits of a manifold and their bores and such conditions often result in leakage with known seal devices.
Effective metal-to-metal sealing is achieved by various types of seal members, and the conical ring type seals marketed by the assignee under the trademarks CONOSEAL and CONOMASTER have proven effective and are widely used, samples of this type of seal ring being shown in the assignee's U.S. Pat. Nos. 2,703,722; 2,992,840 and 3,016,249. Conical seal rings have been used in oil well pipe suspension systems wherein mechanical means for deforming the seal are employed, such as shown in U.S. Pat. No. 4,109,942.
It is known to utilize the pressure within a conduit system to augment retention of interconnected coupling parts, and in U.S. Pat. Nos. 4,084,843 and 4,162,254 apparatus is disclosed wherein retaining members are deformed under the influence of the pressurized medium to prevent a conduit inadvertently separating from a bore.
However, seal assemblies have not been produced which will automatically function in response to pressurizing of the conduit system wherein a metal-to-metal seal is achieved which will not score the receiving bore, and wherein misalignment will not adversely affect the seal.
It is an object of the invention to provide a stab seal assembly wherein a metal sealing element is employed to produce a metal-to-metal seal capable of withstanding high fluid pressures, and yet no scoring of the receiving bore occurs during insertion or removal of the seal assembly and associated conduit.
Another object of the invention is to provide a seal assembly such as used in sub-sea tubing hanger applications which permits limited lateral and angular displacement without affecting the seal.
A further object of the invention is to provide a metal-to-metal seal which is automatically achieved under the influence of the pressurized medium of the conduit system, and wherein no interference fitting is required, and wherein the pressure of the conduit maintains the seal and upon release of the pressure the male stab coupling may be withdrawn from the receiving bore without scoring.
Yet a further object of the invention is to provide a seal assembly which produces an effective seal between a conduit and a receiving bore at various degrees of insertion of the conduit within the bore, and wherein the relationship between the conduit and bore is not critical with respect to the extent of insertion.
In the practice of the invention it is desired to establish a sealed relationship between a cylindrical bore and a conduit which is received within the bore. The conduit includes a seal assembly wherein a conical metal seal ring is interposed between an annular anvil ring and piston ring. Upon the seal assembly being inserted within the bore, and upon pressurization of the system, the piston ring will engage and deform the seal ring in such a manner as to increase the radial dimension of the seal ring to deform the seal ring into metal-to-metal contact with the conduit and bore. Once the seal is established the pressure within the system will maintain the seal ring in engagement with the conduit and bore, and upon release of the pressure of the system, initial withdrawal of the conduit from the bore permits the seal ring to return to its normal relaxed diameter permitting the conduit to be withdrawn from the bore without scoring thereof.
An annular retainer is mounted upon the conduit to maintain the seal assembly thereon, and a releasable wire clip permits the retainer, and assembly, to be removed from the conduit for replacement or maintenance.